The goals of this study will be to investigate the synaptic properties of auditory cortical synapses, in order to assess their putative roles in auditory information processing. The broad objectives of this research are to understand the functional contributions of these projections to auditory perception and behavior and how changes in these synaptic properties manifest with age and in disease processes. I have already identified several anatomical and physiological properties of glutamatergic synapses in the central auditory system, which forms the basis for the proposed investigation. This study will utilize an in vitro slice preparation in the mouse, which has been developed for the auditory cortical pathways. Whole-cell recordings in cortical neurons will be used to record responses to minimal electrical stimulation, photostimulation by uncaging of glutamate, and photostimulation of channelrhodopsin expressing fibers in order to characterize their topographic organization and physiological properties. In addition, a novel method of optical imaging of responses revealed by autofluorescence will be employed to help trace the output patterns of auditory cortical projections. Morphological correlates will be sought using intracellular injections of biocytin. The proposed experiments should lead to further insight on the information-bearing roles of the auditory cortical projections, as well as help to establish their relative weights in the organization of central processing in the auditory system.